This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-070101, filed Mar. 16, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to an autofocus apparatus and a camera.
It is conventionally known that, in a focus adjusting apparatus using a TTL (Through-the-lens) phase contrast detecting method, the focus adjusting accuracy is deteriorated under a specific light source, since chromatic aberration occurs in accordance with the wavelength component of an object light beam.
To cope with the above problem, according to Jpn. Pat. Appln. KOKAI Publication No. 63-168613, a color temperature detecting light-receiving element is provided on the IC chip on which an AF sensor IC serving as a focus detecting light-receiving element is formed. The color temperature detecting light-receiving element measures a color temperature and corrects chromatic aberration.
In the apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 58-86504, a focus detection error due to a color temperature in a focus detecting section including an AF sensor is corrected by means of an output from color temperature measuring means including a light receiving element, a processing circuit and an optical system. The color temperature measuring means are provided separately from the AF sensor IC serving as a focus detecting light-receiving element.
In recent years, single-lens reflex digital cameras using the TTL phase contrast detecting method are sold on the market (xe2x80x9cShashin Kogyo (Photographic Industry)xe2x80x9d, May 1996, pages 42 and 51). In a camera of this type, a light receiving element, a processing circuit and an optical system only for use in color temperature detection are provided separately. White balance is adjusted on the basis of the detected color temperature information.
Jpn. Pat. Appln. KOKAI Publication No. 9-274130 also discloses a digital camera using the TTL phase contrast detecting method.
However, according to the art disclosed in Jpn. Pat. Appln. KOKAI Publication No. 63-168613, a color filter attachment step is required in the process of forming an IC. Therefore, the number of steps is increased, resulting in an increase in costs.
Further, since the apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 58-86504 has the color temperature detecting section for exclusive use, it is necessary to separately provide a light-receiving element, an optical system and a processing circuit only for use in color temperature detection. Therefore, the conventional art has problems that the cost is increased and an additional mounting space is required.
In the single-lens reflex digital cameras, color temperature detecting information is used for white balance adjustment, but not for correction of chromatic aberration in the focus adjustment.
In a digital camera using the TTL phase contrast detecting method disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-274130, correction of chromatic aberration in the focus adjustment is not taken into consideration.
The present invention was made in consideration of the above problems of the conventional art. Its object is to provide a camera comprising a focus adjusting apparatus which can perform accurate focus adjustment by correcting chromatic aberration in focus detection.
To achieve the above object, according to a first aspect of the present invention, there is provided a camera including a photographing lens and a color imaging element, comprising: an autofocus sensor for receiving an object light beam passed through the photographing lens; a focus detecting apparatus for detecting a focus adjusting state of the photographing lens based on an output from the autofocus sensor; a correction calculating circuit for calculating, based on an output from the color imaging element, a correction value for correcting a detection error due to chromatic aberration of the focus detecting apparatus; and a lens driving apparatus for driving the photographing lens based on an output from the focus detecting apparatus and an output from the correction calculating circuit.
According to a second aspect of the present invention, there is provided a camera comprising: a focus detecting light-receiving sensor for receiving an object light beam passed through a photographing lens and a separator lens; a focus detecting circuit for detecting a focus state of the photographing lens based on an output from the focus detecting light-receiving sensor; an imaging element for imaging the object light beam passed through the photographing lens; a correcting circuit for correcting an output from the focus detecting circuit based on an imaging output of the imaging element; and a control circuit for performing focus adjustment based on an output from the correction circuit.
According to a third aspect of the present invention, there is provided a camera including a photographing lens and a color imaging element, comprising: an autofocus sensor for receiving an object light beam passed through the photographing lens; focus detecting means for detecting a focus adjusting state of the photographing lens based on an output from the autofocus sensor; correction calculating means for calculating, based on an output from the color imaging element, a correction value for correcting a detection error due to chromatic aberration of the focus detecting means; and a lens driving apparatus for driving the photographing lens based on an output from the focus detecting means and an output from the correction calculating means.
According to a fourth aspect of the present invention, there is provided a camera comprising: a focus detecting light-receiving sensor for receiving an object light beam passed through a photographing lens and a separator lens; focus detecting means for detecting a focus state of the photographing lens based on an output from the focus detecting light-receiving sensor; an imaging element for imaging the object light beam passed through the photographing lens; correcting means for correcting an output from the focus detecting means based on an imaging output of the imaging element; and control means for performing focus adjustment based on an output from the correcting means.
According to a fifth aspect of the present invention, there is provided a camera having an autofocus apparatus, comprising: an autofocus sensor for receiving an object light beam passed through a photographing lens; defocus calculating means for calculating an amount of defocus based on an output from the autofocus sensor; a memory for storing a plurality of correction values to correct a detection error due to chromatic aberration of the autofocus apparatus; a color imaging element for imaging an object; selecting means for selecting at least one of the plurality of correction values stored in the memory based on color information output from the color imaging element; defocus correcting means for correcting the amount of defocus by the correction value selected by the selecting means; and a lens driving apparatus for driving the photographing lens based on an output from the defocus correcting means.
According to a sixth aspect of the present invention, there is provided an autofocus apparatus of a camera, comprising: an autofocus sensor; defocus calculating means for calculating an amount of defocus based on an output from the autofocus sensor; a memory for storing a plurality of correction values to correct a detection error due to chromatic aberration of the autofocus sensor; a color imaging element; color temperature determining means for determining a color temperature of an object light beam based on an output from the color imaging element; selecting means for selecting at least one of the plurality of correction values stored in the memory based on an output from the color temperature determining means; and defocus correcting means for correcting the amount of defocus by the correction value selected by the selecting means.
According to a seventh aspect of the present invention, there is provided a camera comprising: a photographing lens for focusing an object light beam; a color imaging element for receiving the object light beam; an autofocus sensor for receiving the object light beam passed through the photographing lens; a focus detecting section for detecting a focus adjusting state of the photographing lens based on an output from the autofocus sensor; a correcting section for correcting a detection error due to chromatic aberration of the focus detecting section based on an output from the color imaging element; and a lens driving section for driving the photographing lens based on an output from the focus detecting section and an output from the correcting section.
According to an eighth aspect of the present invention, there is provided a camera comprising: a photographing lens for focusing an object light beam; a color imaging element, having a plurality of color temperature detecting regions, for receiving the object light beam; an autofocus sensor for receiving the object light beam passed through the photographing lens; a focus detecting section, having a plurality of focus detecting areas, for detecting a focus adjusting state of the photographing lens based on an output from the autofocus sensor in each area; a correcting section for calculating a color temperature evaluation value based on an image signal in a color temperature detecting region, and correcting a detection error due to chromatic aberration of the focus detecting section based on the color temperature evaluation value; and a lens driving section for driving the photographing lens based on an output from the focus detecting section and an output from the correcting section.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.